1. Technical Field
The present invention relates to a plasma display panel and, more particularly, to a plasma display panel having enhanced luminous efficiency by improving the structures of sustain electrodes and dielectric layers.
2. Related Art
Plasma display panels (PDPs), which form images using an electric discharge, are widely used due to their excellent performance in such characteristics as brightness and viewing angles. The gas discharge is performed between electrodes by an alternating current (AC) voltage or a direct current (DC) voltage applied to the electrodes, and then visible light is emitted from a fluorescent layer that is excited by ultraviolet light created when the gas discharge is performed.
Plasma display panels are categorized into DC types and AC types according to the discharge type. In DC type plasma display panels, all of the electrodes are exposed to a discharge space, and electric charges move directly between the corresponding electrodes. In AC type plasma display panels, at least one electrode is covered by a dielectric layer and discharge is performed by a wall charge, not by the migration of electric charges between the corresponding electrodes.
Plasma display panels are also categorized into a facing discharge type and a surface discharge type according to the structural arrangement of the electrodes. In the facing discharge type plasma display panel, each pair of sustain electrodes is separately disposed on a front substrate and a rear substrate, and discharge occurs in a direction perpendicular to the substrates. In the surface discharge type plasma display panel, each pair of sustain electrodes is disposed on the same substrate, and discharge occurs in a direction parallel to the surface of the substrate.
The facing discharge type plasma display panels have high luminous efficiency but have a defect in that a fluorescent layer is likely to be deteriorated by plasma. Therefore, the surface discharge type plasma display panels are mainly used.
The plasma display panel includes a rear substrate and a front substrate which face each other. A plurality of address electrodes are arranged in stripes on an upper surface of the rear substrate, and the address electrodes are covered by a first dielectric layer. A plurality of partition walls is formed on an upper surface of the first dielectric layer to prevent electric and optical interference between discharge cells. Inner surfaces of the discharge cells partitioned by the partition walls are coated with fluorescent layers colored in red (R), green (G), and blue (B) to a predetermined thickness, respectively. In general, the interior of the discharge cells is filled with a gaseous mixture composed of neon (Ne) and xenon (Xe).
The front substrate, which is transparent so that visible light can pass through it, is usually made of glass, and is combined with the rear substrate having the partition walls. Sustain electrodes, which are in pairs, are arranged in stripes on a lower surface of the front substrate, and the sustain electrodes cross the address electrodes at right angles. The sustain electrodes are formed of transparent conductive materials such, as indium tin oxide (ITO), which allow visible light to pass through them. Metallic bus electrodes having a narrower width than the sustain electrodes are formed on a lower surface of the sustain electrodes. The sustain electrodes and the bus electrodes are covered by a second dielectric layer, which is transparent, and a protective layer is formed on a lower surface of the second dielectric layer. The protective layer protects the second dielectric layer from being damaged by sputtering of plasma particles, and emits secondary electrons to lower the discharge voltage. In general, the protective layer is formed of magnesium oxide (MgO).
The driving of a plasma display panel having the above configuration is divided into driving an address discharge and driving a sustain discharge. The address discharge occurs between an address electrode and a sustain electrode, thereby forming a wall charge. The sustain discharge occurs as a result of a potential difference between sustain electrodes. When the sustain discharge occurs, a fluorescent layer in contact with the corresponding discharge cell is excited by ultraviolet light emitted from the discharge gas, thereby emitting visible light. The visible light passes through the front substrate forming images that can be recognized by a user.